Orrin Hatch is conservative by almost any measure, but these days that’s not enough to shield him from the right. There’s a credible challenger in the wings and a real possibility that the Utah senator could become the first establishment casualty of the 2012 season.

The Tea Party movement first demonstrated its clout last year by knocking off Hatch’s Utah colleague, Bob Bennett. Now the movement’s activists have served notice that they are displeased with several big-name Republican senators. Hatch, like most of them, is cultivating the grassroots, moving rightward, and hoping to fend off a serious primary challenger.

What all this amounts to is nothing less than a redefinition of conservatism—or, at least, the brand of conservatism acceptable to those who have the power to boot Republicans who have long toed what used to be the party line. The no-longer-acceptable column includes a willingness to negotiate or form partnerships with Democrats, or even to back the aims of the last Republican president.

Some of Cornyn’s primary picks—remember Charlie Crist?—didn’t fare so well in 2010. But a wholesale housecleaning of GOP incumbents before the general election looks unlikely for now. One reason is the lesson of 2010, not just for senators trying to preserve their careers but also for the conservative groups deciding where to focus their money and activism.

Viability is a watchword for FreedomWorks and the Club for Growth, two of the three juggernauts that use similar criteria for their primary picks. As for the third, the Tea Party Express, founding strategist Sal Russo told me his group is willing to back candidates with “a tougher course” to victory, but “clearly we’re trying to win elections.”

Hatch has a solidly conservative lifetime rating of 89 from the American Conservative Union. But the logic of campaigns is narrow and sometimes unfair. Hatch is from a state so Republican that anyone who could best him for the nomination would be a near shoo-in in a general election (unlike, say, swing state Nevada or Democratic-leaning Delaware). And Chaffetz is eminently credible.

The Club for Growth endorsed Angle last year but was disappointed in her general-election campaign. “When you’re on that big a stage and you’ve got that many people offering you help, we were hopeful that she might have taken some of it,” Club President Chris Chocola told me.

While Chocola defends the Angle endorsement, it’s notable that his first pick against an incumbent this time around is Chaffetz, promising him money in a recent email headlined “Run Jason Run.” “If we make an endorsement, we ask our members to invest their money. We’re not going to ask our members to do that if we don’t think a candidate’s viable,” Chocola says.

Utah has a multi-tiered nomination process that starts with neighborhood caucuses, proceeds to a convention, and then, if no candidate wins 60 percent of delegates, to a primary. Utah strategists and Hatch insiders say the senator has been reaching out to the new Tea Party activists in his state for years and is building a strong organization. “I intend to win, and we will win,” he told conservative radio host Hugh Hewitt. He dismissed Chaffetz as a publicity hound, adding, “I think he could possibly be a halfway decent congressman in the House if he would concentrate on it.”

Many of Hatch’s alleged sins, as reeled off by Chaffetz and the Club for Growth, involve his support for such George W. Bush initiatives as TARP (the bank bailout), the Medicare prescription-drug benefit and the No Child Left Behind education act. He also backed earmarks (unfashionable these days), raising the debt ceiling (once considered a responsible vote to avoid default), and a 2007 extension of the State Children’s Health Insurance Program. Hatch was not an outlier on the children’s health program—17 GOP senators voted yes—but that was the least of it. Ten years earlier he had joined Ted Kennedy to create it.

Hatch, who declined a Daily Beast interview request, has apologized in a half-hearted way for his TARP vote; introduced a balanced-budget bill with fellow Utah Sen. Mike Lee; and insisted on spending cuts as a condition for raising the debt limit. “Anybody who says I’m no fiscal conservative is, I don’t want to be rude, but they’re lying,” Hatch told Hewitt. But Chocola says “Utah can do better.” FreedomWorks, which helped Lee oust Bennett in 2010, also anticipates being active in Utah this year. Meanwhile Lee, a Tea Party favorite, has said he won’t endorse Hatch.

One of Hatch’s selling points to voters is that he’s in line to chair the Finance Committee if Republicans take over the Senate—no small matter since the panel handles taxes, trade, Medicare, Medicaid, and Social Security. Chaffetz is not impressed. “If you’re not voting right,” he told me, “seniority doesn’t matter.”

He says Hatch was “swept in” with Jimmy Carter in 1976 after a campaign in which Hatch asked Utah voters, “What do you call an 18-year senator? You call him home.” Hatch already has been in office twice as long as that long-ago opponent and wants to stretch it to 42 years with a seventh term. “It’s time for a new generation to take a stab at these problems,” Chaffetz says.

Indiana is another hotbed of unrest. Most of the state’s GOP establishment has endorsed Mourdock and all three national groups are looking at the race. Lugar, facing what conservative “Hoosier Pundit” blogger Scott Fluhr habitually calls “Lugargeddon,” has removed his name from the DREAM Act to help children of illegal immigrants. He recently signed on to a bill to replace the income tax with the “fair tax,” a national sales tax.

How’s it playing? Russo says Lugar “continues to express his hostility” toward the Tea Party movement. FreedomWorks also expects to play in Indiana. The Club for Growth is still cogitating after what Chocola called “a disappointing first quarter” in Mourdock fundraising. “Mourdock needs to prove he can raise the resources to be competitive,” he says.

Snowe, who won her 2006 race with an astonishing 74 percent of the vote, is the most liberal of the quintet. She was a crucial vote for President Obama’s stimulus program in 2009 and supported a health-reform bill in committee. Just recently she voted against the budget pushed by Paul Ryan, expressing concern about its plan to turn Medicare into a voucher program. It can’t hurt Snowe to cast herself as a protector of the medical program for the elderly in a state with the highest median age. Nor does it hurt that Maine’s Tea Party governor, Paul LePage, has endorsed her. It’s personal; her first, late husband helped the dirt-poor, French-speaking teenager get into college, and he has never forgotten.

So far Snowe has two challengers hoping to capitalize on conservative frustration: Scott D’Amboise, a small businessman aligned with the Tea Party, and Andrew Ian Dodge, who heads Maine Tea Party Patriots. Neither is getting much traction. “I don’t think either one of them is electable,” says Pete Harring, founder of MaineTeaParty.com. “I honestly don’t see anybody in the state strong enough to overthrow Olympia Snowe.” Russo praised Snowe for backing a balanced-budget amendment and repeal of Obama’s health law. The Tea Party Express is “open to her seeing the light,” he says.

Corker, who has negotiated with Democrats over financial reform and auto bailouts, is a top target of RedState.com founder Erick Erickson. “He pushes the Senate GOP left and toward capitulation. He is contemptuous of conservatives,” Erickson wrote last month. Yet Corker fits squarely in his state’s bipartisan tradition of centrists, and so far no challenger has surfaced.

The same is true in Massachusetts, where Brown won a stunning upset last year for Kennedy’s old seat. “I find it hard to believe you could do much better than Scott Brown in Massachusetts,” says Adam Brandon, a spokesman for FreedomWorks. “Maybe you could prove me wrong. That’s the unknown. What is known is that we could have the ground game in Utah and Indiana to be successful.”

That’s pragmatism talking. There’s been no donning of hair shirts over 2010, even from Russo, whose group backed the losing Angle-O’Donnell-Miller trifecta (he says the candidates weren’t “as bad as some people said they were”). But will these groups go to the mat next year for conservative challengers who are inexperienced or erratic, who display sub-par fundraising, communication, or organizational skills, in hard-to-win liberal or moderate states? Probably not. For the moment, at least, it seems the maturing Tea Party movement has raised the bar.

Jill Lawrence is an award-winning journalist who has covered every presidential election since 1988. Most recently, she was a senior correspondent and columnist for PoliticsDaily.com. Her other positions have included national political correspondent for USA Today and national political writer at The Associated Press.